Skip to main content
U.S. flag

An official website of the United States government

Here’s how you know

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

HTTPS

Secure .gov websites use HTTPS
A lock (LockA locked padlock) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

    • Environmental Topics
    • Air
    • Bed Bugs
    • Cancer
    • Chemicals, Toxics, and Pesticide
    • Emergency Response
    • Environmental Information by Location
    • Health
    • Land, Waste, and Cleanup
    • Lead
    • Mold
    • Radon
    • Research
    • Science Topics
    • Water Topics
    • A-Z Topic Index
    • Laws & Regulations
    • By Business Sector
    • By Topic
    • Compliance
    • Enforcement
    • Laws and Executive Orders
    • Regulations
    • Report a Violation
    • Environmental Violations
    • Fraud, Waste or Abuse
    • About EPA
    • Our Mission and What We Do
    • Headquarters Offices
    • Regional Offices
    • Labs and Research Centers
    • Planning, Budget, and Results
    • Organization Chart
    • EPA History

Breadcrumb

  1. Home
  2. Risk Management Program (RMP) Rule

Atmospheric conditions used for off-site consequence analyses

What atmospheric conditions must a source assume when performing the offsite consequence analyses required under 40 CFR Part 68, Subpart B?

For the worst-case release analysis, 1.5 meters per second wind speed and F atmospheric stability class must be assumed, unless the stationary source owner or operator can demonstrate that local meteorological data applicable to the stationary source show a higher minimum wind speed or less stable atmosphere at all times during the previous three years (40 CFR §68.22(b)). For releases of regulated toxic substances, the owner or operator must also use the highest daily maximum temperature and the average humidity for the site during the past three years. Owners and operators using the RMP Offsite Consequence Analysis Guidance will assume 25 degrees Celsius and 50 percent humidity (40 CFR §68.22(c)).

For the alternative release scenario, the owner or operator should use the typical meteorological conditions (i.e., wind speed and atmospheric stability) for the stationary source (40 CFR §68.22(b)), as well as typical temperature and humidity data gathered at the stationary source or at a local meteorological station (40 CFR §68.22(c)). Owners and operators using the RMP Offsite Consequence Analysis Guidance will assume 3 meters per second wind speed, D atmospheric stability class, 25 degrees Celsius and 50 percent humidity.

Risk Management Program (RMP) Rule

  • About RMP
    • Publications
    • Training Resources
    • Frequent Questions
  • Guidance and Fact Sheets
    • Guidance for Facilities
    • Guidance for Implementing Agencies
    • Guidance for Inspections
  • Submitting an RMP
    • RMP*Comp
    • RMP*eSubmit
      • RMP*eSubmit User's Manual
    • Resubmit, Correct or Withdraw
  • Accessing RMP Information
    • Federal Reading Rooms
    • Vulnerable Zone Indicator System
  • General Duty Clause
Contact Us about the Risk Management Program Rule
Contact Us to ask a question, provide feedback, or report a problem.
Last updated on May 6, 2025
  • Assistance
  • Spanish
  • Arabic
  • Chinese (simplified)
  • Chinese (traditional)
  • French
  • Haitian Creole
  • Korean
  • Portuguese
  • Russian
  • Tagalog
  • Vietnamese
United States Environmental Protection Agency

Discover.

  • Accessibility Statement
  • Budget & Performance
  • Contracting
  • EPA www Web Snapshot
  • Grants
  • No FEAR Act Data
  • Plain Writing
  • Privacy
  • Privacy and Security Notice

Connect.

  • Data
  • Inspector General
  • Jobs
  • Newsroom
  • Regulations.gov
  • Subscribe
  • USA.gov
  • White House

Ask.

  • Contact EPA
  • EPA Disclaimers
  • Hotlines
  • FOIA Requests
  • Frequent Questions
  • Site Feedback

Follow.

Environmental Protection Agency logo
www.epa.gov Feedback Survey

Welcome! Please share your feedback on how we can make www.epa.gov work better for you.

A red asterisk (*) indicates a required field.

Success

Thank you. Your feedback has been received.

Error

alert message

Required Questions - page 1 of 2
question_55203_answer_01
*

400 characters allowed
Would you like to take two more minutes to answer more questions to help us improve our services?
Yes, keep going →
← Back
Optional questions - page 2 of 2
How would you describe yourself?
400 characters allowed
400 characters allowed
400 characters allowed
U.S. flag

An official form of the United States government. Provided by Touchpoints
OMB Approval #1090-0008 · Expiration Date 11/30/2027